acidogenic bacteria. Jiang et al. (2013) reported that the VFAs
accounted for 6.6% at pH uncontrolled around 3.0 for food waste
treatment in batch experiment. Dog˘ an and Demirer (2009) found
that the ratio of acid produced to sCOD was approximately 19.1%
at pH uncontrolled for municipal solid waste treatment.
However, in this study the concentration of tCODp was
23.5 gCOD/L and then the ratio of tCODp/sCOD was high to
84.1%. Wang et al. (2014) found that the maximum VFAs concen-trations at pH 4.0 was only 2.9 gCOD/L, however, high concentra-tion of 18.50 g/L lactic acid was also produced at pH of 4.0. Lactic
acid with concentration of approximately 9.0 g/L was also found
at uncontrolled pH in batch experiment ( Kim et al., 2003).
Therefore, lactic acid was an indispensable fermentation product
at pH of 4.0 for FVWs treatment and the acidogenic bacteria still
maintained relatively high activity at low pH of 4.0